The Oakland native (above) gets to eat home-cooked meals, sleep in his own bed and hang out with high-school buddies. He also saves on rent, meaning he can devote more of his league-minimum $400,000 salary to video games.

“This cuts out all the hard stuff, like setting up cable and getting furniture,” he says.

League officials say many players head home over the winter, but they believe that only Mr. Ross and Neil Walker, of the Pittsburgh Pirates, return to the nest during the season.

That gives Mr. Ross a unique understanding of what it’s like to throw 95-mile-per-hour fastballs in front of 20,000 cheering fans and then go see the movie “Toy Story 3″ with his mother, as he did last month.

“He’s up in that elusive tax bracket, and he’s still with mom and dad?” says fellow A’s pitcher Dallas Braden, 26, who hails from nearby Stockton, Calif., but has his own house. “I would tell him to utilize these things we call banks,” says Mr. Braden.